The effects of MS₂ (M = Mo or W) substrates on electronic properties under electric fields in germanene-based field-effect transistors

Abstract

Germanene has attracted significant attention due to its novel electronic properties and strong spin-coupling effect. However, the tiny band gap of the germanene dramatically limits its application in field-effect transistors (FETs). Inspired by the utilization of the substrates and electric fields to adjust the band gaps of two-dimensional materials, we investigated the fundamental mechanism of electric fields on the atomic structures and electronic properties of germanene supported by MS2 (M = Mo or W) substrates through first-principles calculation. The results show that the substrates can induce a symmetry breaking in the germanene sublattice via van der Waals interaction, leading to a sizable band gap at the Dirac point. In addition, the band gaps of the germanene/MS2 heterostructures can be effectively modulated by applying an external electric field. Under suitable electric fields, the considerable band gap values of CMo germanene/MoS2 and TGeL-W germanene/WS2 configurations can open the maximum band gaps with 263 and 247 meV, which satisfy the requirements of FETs at room temperature. Meanwhile, the evolutions of charge transfers under electric fields were explored to illustrate how electric fields and substrates promote the electronic properties of germanene. More interestingly, a Schottky–Ohmic transition can occur when a specific electric field is imposed on the germanene/MS2 heterostructures. Note that the hole and electron carrier mobilities of germanene/MS2 heterostructures are still significantly preserved, showing some superior electronic performances than some heterostructures. The results provide a critical theoretical guide for improving the electronic properties of germanene, and demonstrate the designed germanene/MS2 heterostructures with the tunable band gaps and higher carrier mobilities as germanene-based FETs.

A DFT study of superior adsorbate–surface bonding at Pt-WSe2 vertically aligned heterostructures upon NO2, SO2, CO2, and H2 interactions

“…The Perdew–Burke–Ernzerhof (GGA-PBE) generalized approximation is utilized to handle electron exchange correlation accurately 34 , 35 . The study incorporates Density Functional Theory with dispersion (DFT-D) and van der Waals (vdWs) interactions to enhance accuracy, addressing the traditional DFT’s challenges in capturing weak forces 36 , 37 . Tkatchenko and Scheffler’s (TS) method is applied for precise simulation of vdWs interactions 38 , 39 .…”

First-Principles Investigation of Transition Metal (Co, Rh, and Ir)-Modified WS2 Monolayer Membranes: Adsorption and Detection of SF6 Decomposition Gases

“…Chen et al found that the pom-pom WS 2 showed high linearity ( R 2 > 0.99) for four decomposed gases, namely H 2 S, SO 2 , SOF 2 , and SO 2 F 2 , at a low concentration (50 ppm). Wang and coworkers found that an increase in oxygen content led to an increase in response time for SO 2 and SO 2 F 2 (24 and 26 s). However, the recoverability of WS 2 -based gas sensors in prior investigations remains inadequate.…”

“…Transition metal dichalcogenides (TMDCs) are currently causing a stir in the gas field due to their outstanding semiconductor performance, abundant porosity, and layered structure. − Among these materials, WS 2 stands out with its small band gap of 2.231 eV and high room-temperature carrier mobility (monolayer >20 cm –1 V –1 s –1 ), making it superior to other TMDCs. , Recent experimental investigations have unveiled the promise of employing intrinsic WS 2 for detecting SF 6 decomposition gases, highlighting its inherent capabilities in this realm. Chen et al found that the pom-pom WS 2 showed high linearity ( R 2 > 0.99) for four decomposed gases, namely H 2 S, SO 2 , SOF 2 , and SO 2 F 2 , at a low concentration (50 ppm).…”